Connections of electrical cable, wherein two ends of different cables are joined by an electrically conductive connector or a cable end is terminated by connection to a device such as a lug for connection to a bus, must be protected from the environment and electrically insulated so that the connection is electrically isolated. One method of protecting the connection is to provide a resilient, elastomeric tube which has an inner diameter approximately that of the connection and force the tube over the connection.
The difficulty arises in forcing the tube along the cable and over the connection. The preferred material for the elastomeric tube is silicone rubber, although other elastomers may be used. Silicone and other elastomers have a relatively high surface friction, thus a tube made from these materials does not slide easily relative to the cable and powdered or other lubricants such as oil or grease must be used to achieve assembly of the tube to the connection. This method is extremely messy and requires considerable cleaning by the assembler of his or her person and the cable after the tube has been assembled to the cable.
To avoid the use of separate lubricants, manufacturers including Varflex Corporation of Rome, N.Y., U.S.A. and Markel Corporation of Norristown, Penna., provide flexible tubular products which are braided from cotton, rayon, nylon, glass or other fibers, and impregnated, coated, or impregnated and coated with an electrical insulating material such as the silicone rubber discussed above. Thus, in this construction, the tube comprises an inner core of braid which is permanently and intimately attached to a covering jacket of insulating material. The braided core permits the insulating material to be slid over an object such as an electrical wire because the braid acts as a solid lubricant for the higher friction insulating material.
While this construction is effective to permit the insulating material to be easily assembled to a small wire, there are drawbacks associated with the construction. Since the braided core and the jacket are integral, the braided core is always exposed at the ends of the tube. This permits fluids to be drawn into the tube by a wicking action unless the ends are sealed by some means such as tape. It is also noted that these products are only available in small sizes, i.e., less than approximately 10 mm in diameter, so the applicability of these products to large objects, such as large diameter electrical cable, is questionable.
It is therefore an object of this invention to provide means for facilitating the assembly of a resilient, elastomeric, protective tube to an electrical cable, or, more generally, an elongated object to be protected, without the use of powdered or fluid lubricants and to ensure that the protective tube seals the object from contaminants.